1. Technical Field of the Invention
The invention relates to compounds and compositions for the reduction of hydrogen charging and hydrogen induced cracking of steels.
2. Related Art
The prior art includes mostly the development and use of inhibitive compounds and compositions for the lowering of the volume loss corrosion rate of steels in corrosive environments. Inhibitor compounds and compositions for use in commercial formulations are selected for their high level of "inhibitor efficiency" as defined solely by the magnitude of reduction in the volume loss corrosion rate produced by the application of the inhibitor compound and/or composition to the environment.
The only prior art describing the use of inhibitors to prevent cracking involves mitigation of stress corrosion cracking ("SCC") in various alloys and environmental systems. However, the process of SCC is different than hydrogen induced cracking ("HIC"). SCC is mechanistically a processes of localized corrosion concentrated and propagated by application of a tensile stress. Hydrogen produced by corrosion is not a factor in this type of cracking.
The prior art has been highly focused on the inhibition of volume loss corrosion and to a lesser degree SCC. No prior art shows a reduction in hydrogen charging characteristics producing a long term elimination or major reduction in hydrogen charging and most importantly HIC in steels. More specifically, there have been no chemical compounds or compositions identified that provide such protection.
The extent of the problem is two fold: (1) new equipment has fresh metal surfaces that will initially corrode very rapidly to produce high levels of hydrogen charging and HIC, and (2) older equipment after surface cleaning used for I.D. inspection removes the normally formed protective I.D. films and leaves fresh metal surfaces which can also produce high levels of hydrogen charging and HIC. The application of the present inventive compounds and compositions reduce both high hydrogen charging situations and greatly reduce the occurrence of HIC in such equipment.